Shaped charge liners



March 26, 1968 LE ROY WYMAN, sR.. ETAL 3,375,103

SHAPED CHARGE LINERS Original Filed April 30, 1964 INVENTOR! L m 3 0 N mw m Z w mdfl A db mbrr y b 001V m, P mE LEE. u/a

United States atet 3,375,108 SHAPED CHARGE LINERS Le Roy Linwood Wyman, Sr., Bethesda, and John C. Everts, Bowie, Md., and Rolla Estus Pollard, deceased, late of Kensington, Md., by Mabel Pollard, executrix, Kensington, Md., assignors to the United States of America as represented by the Secretary of the Army Original application Apr. 30, 1964, Ser. No. 364,891. Divided and this application Aug. 10, 1965, Ser. No. 487,952

6 Claims. (Cl. 75 202) ABSTRACT F THE DISCLOSURE A method for the preparation of a shaped charge liner in which a powdered high refractory material is fed through a floating die to a cavity provided by an inverted conical mold, compressed and sintered to form a porous unitary hollow shaped charge liner and thereafter removed from the mold; the pores of the liner are infiltrated or densified with a ductile metal at .a temperature below the sintering temperature but above the melting point of the metal for maximum densification so that on firing the shaped charge the liner will collapse to form a jet of comminuted particles directed at a target, with the re-frectory material making the hole in the target and the ductile metal impregnating the walls for a smooth hole.

This is a division of application Ser. No. 364,891 filed Apr. 30, 1964.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to an improvement in hollow shaped charges utilized in explosive devices, projectiles or oil wells to increase the destructive effect thereof.

Current theories as to the effectiveness of metallic materials for shaped charges or liners therefor, while differing widely in concept and in practice, appear to be compatible with test results which indicate that such materials of high densities and mechanical properties give prefer-able performances. Due to their inherent characteristics, the more dense and stronger metals, ie the refractory metals in general, while seemingly the more preferable for shaped charge liner materials are not readily amenable to conventional methods of fabrication into such shapes as those generally used for hollow charges or liners.

It is the object of this invention to utilize such refractory materials for shaped charge liners, components thereof, or appendages to such liners for after effect.

It is a further object of this invention to provide a method of treatment of these refractory metals or compounds which make them suitable for fabrication into shapes used for such charges.

Materials, suitable for the shaped charge or liner of this invention, are cemented or bonded refractory metals such as tungsten, titanium, or zirconium, their carbides, borides, or nitrides, and are employed as refractory materials as difierentiated from frangible materials heretofore used. These materials, less critical to wartime economy, may be used for cone production by employing methods of treatment based primarily on powder metallurgy techniques including infiltration, milling, pre-alloying, co-precipitation and slip-casting processes. This is accomplished by forming a cone by compressing a loose refractory powder in a mold using a compression ratio of 3 or 4 to 1. Since metal powders do not flow under pressure and the compression thereof must be accomplished by essentially uni-directional pressure and action, without generating shearing stresses that will result in a cracked compact.

For a better understanding, reference is made to the accompanying drawing in which,

FIGURE 1 is a diagrammatic representation of the die,

FIGURE 2 is a representation of a projectile with a shaped charge therein, and

FIGURE 3 shows a projectile with a shaped charge having a supplementary shaped charge behind the apex of the main shaped charge for additional destructive effect.

In this preparation of a hollow shaped charge liner, the material selected may be intimately ball milled into powder form and fed into a floating die 10 having a presser cavity therein as shown in FIGURE 1. The male plunger 11 which defines the inside of the powdered cone 12 and the face of the cone flange 13 is temporarily secured to the floating die 10 while defining the bottom of the form. The angle at the apex of the cone 12 may vary according to various designs of shaped charges, but the preferable shape for military applications such as the 57 mm., the cone has an apex angle of 4042. The female plunger 14, which is the top of the form defines the outer surface of the cone 12 and the flange 15, and is spaced the desired distance from the male plunger 11 which is also temporarily secured to the die 10. The female plunger 14 has a channel 16 through which is fed the powdered refractory material for the formation of the conical shell of the shaped charge. When the channels between the plungers 11 and 14 are filled with the powdered material to a point slightly above the apex of the cone, the central plunger 17 is inserted to close the channel 16 and is secured to the plunger 14. The plungers 11 and 14 released from the floating die 10, are now free to act in opposition to compress the powdered cone and the powdered material is subjected to a suitable pressure, such as at least 150,000 lbs. for 57 mm. cone. Since the action between the two plungers exerts a shearing stress, the pressure should be less than that required to shear and crack the cone, particularly at the flange. After being properly compressed the plungers are removed and the pressed cone is pushed out of the die hydraulically or by any suitable means.

The pressed cone is then sintered in a non-oxidizing atmosphere and at a temperature suflicient to cause an intergrowth of the pressed metal powder particles which results in a solid mass and shows upon microscopic examination the formation of tiny pores within the structure. The density of this structure is dependent on the powder characteristics of the material selected. The creation of this porous structure in the sintered material is vital in that it permits the infiltration or loading of the material with a ductile metal. The sintered cone with the tiny pores may be further densified by the infiltration of a ductile metal such as copper, lead or cobalt in a molten or liquid state to fill these pores. This is accomplished by further sintering the cone in the presence of the ductile metal at a temperature that is below the first sintering temperature but sufficient for the ductile metal to be in a molten or liquid condition, which on cooling produces a cone of metal of near-maximum density in an annealed condition.

If for example, tungsten is selected as the material, the powdered tungsten is compressed into a hollow conical shell as heretofore described and the shell is placed in a suitably designed container, introduced into a temperature controlled furnace having a non-oxidizing atmosphere and sintered at any suitable temperature below its melting point to form a solid cone having tiny pores therein. The cone is then infiltrated with a metallic copper in any suitable manner by reheating the cone and the copper to a temperature near or above the melting point of the ductile metal. The copper having free access to the properly heated tungsten shell thereby infiltrates theporous cone to form upon cooling a solid, dense, partially ductile refractory liner. The infiltrating metal need not enter into metallurgical reaction with the metal of the porous cone, but must have sufiicient fluidity and surface tension to wet the porous cone and thereby be adsorbed. This liner may be composed of 80% metal (tungsten) and of the ductile metal (copper), the content of the .latter being dependent upon the porosity of the tungsten cone.

Generally, the infiltration of the lower melting metal is accomplished with practically no metallurgical reaction as in the case of powdered iron or steel pressed cones which are infiltrated with copper while on the other hand there may be a metallurgical reaction as in the case of a powdered copper cone infiltrated with tin to form bronze cones or with zinc to form brass cones. These are examples of what may be accomplished by various combinations of cone-skeleton and infiltrant to obtain a similar result regardless of whether there be any metallurgical reaction in the infiltration step.

Alternately, this liner may also be made by intimately ball milling a refractory material, such as tungsten carbide in powder form with a ductile metal, such as cobalt in powder form, until the components are adequately integrated. This mixture of powders may be compressed as before described in a cone, sintered at a temperature below the melting point of the refractory material but near or above the melting point of the bonding metal and densified by a subsequent coining operation which consists of repressing in a suitably designed die or reshaping. This may be followed by resintering, or it may be succeeded by repeated coining and sin-tering, resulting in a substantially solid cone of near-maximum density in an annealed condition depending on the product desired and whether the coining or resintering is the final operation. The mechanical properties of this tungsten carbide-cobalt conical shell may be varied from near-brittle (cobalt in this instance) contents of the order of 3%, to semimalleable contents of some 20 to or over.

It should be understood that either approach heretofore described for the preparation of the powdered materials may be utilized within the scope of this process.

The refractory materials which have been tested and found amendable to this treatment are tungsten, titanium or zirconium, their carbides, borides or nitrides densified with a ductile metal which may be either copper, lead or cobalt.

The shaped charge of this invention may be utilized in any capacity in which such charges are employed, but it is particularly adapted for use as a supplementary charge in a projectile. Such an arrangement is represented in FIGURE 2, in which the projectile 18 has .an impact fuze 19 in the ogive thereof, and a hollow shaped charge 12 made of refractory material with a detonator 20 shown positioned therein at the apex of the charge.

FIGURE 3 shows diagrammatically the shaped charge 12 made of the refractory material of this invention, and an appendage or second shape-d charge 21 also made of similar mate-rial but smaller than the preceding charge, and having a detonator fuze 22. Assuming the true action of a hollow shaped charge is the inversion of the cone, it can be readily seen that the supplemental charge 21 greatly adds to the resultant destructive eifect of the projectile on impact. By reason of the powder metallurgy used in the shaped charge of this invention, it also becomes possible to achieve a measure of additional antipersonnel effect by incorporating within the cone, or appendage thereto, ingredients which will follow the jet penetration action of the cone by pyrotechnic effect, toxic effects or both.

The production of the shaped charge of this invention and the method of forming such a charge may readily be streamlined in emergencies, since all of the operations are amenda ble to high speed continuous operation, mostly mechanized, this materially conserving on critical machine tool equipment and trained operators.

What is claimed is: g

1. A method of forming a hollow shaped charge liner comprising, compressing a powdered refractory metal in a die to form a hollow cone shaped charge liner, sintering the pressed hollow linerat a temperature below the melting point of the refractory metal, infiltrating the sintered pressed hollow liner with 3 to 25% of a molten ductile metal to increase the density and cooling the infiltratcd pressed cone to produce a hollow shaped charge liner of near maximum density.

2. A method of forming a hollow shaped charge liner of powdered material comprising, filling the hollow cone shaped form made by two opposing plungers operable in a floating die with a powdered refractory metal through the die, compressing the powdered refractory metal between the plungers to 'form a hollow shaped chargelin'er, removing the hollow liner from the die, sintering the pressed hollow liner at a temperature below the melting point of the refractory metal, infiltrating the sintered pressed hollow liner with 3 to 25 of a molten ductile metal to increase the density and cooling the infiltrated pressed liner to produce a hollow shaped charge liner of near maximum density.

3. A method of forming a hollow shaped charge liner comprising, compressing in a die to form a hollow cone shaped charge liner of a powdered refractory material selected from a group consisting of tungsten, titanium, zirconium, the carbides, the borides and the nitrides of each metal, removing the :hollow liner from the die, sin- 7 ering the pressed hollow liner at a temperature below the melting point of the refractory material, infiltrating the sintered pressed hollow cone to increase the density with 3 to 25 of a molten metal selected from a group consisting of copper and lead and cooling the infiltrated pressed liner to produce a hollow shaped charge liner of near maximum density.

4. A method of forming a hollow shaped charge liner from powdered material comprising, mixing a powdered refractory metal and a powdered ductile metal of lower melting point to form an integrated mixture, filling through a die to the mold with the powdered mixtureto form a hollow cone shaped charge liner, subjecting the cast powdered mixture in the die to a pressure of at least 150,000 lbs. to form a hollow pressed liner, removing the pressed liner from the die, sintering the pressed liner at a temperature between the melting points of the refractory metal and the ductile metal in a non-oxidizing atmosphere to produce a porous structure of the refractory metal of the liner infiltrated with the molten ductile metal and cooling the infiltrated pressed liner to produce a hollow shape-d charge liner of high density.

5. A method of forming a hollow shaped charge liner from powdered material comprising, milling a mixture of a powdered refractory material selected from a group consisting of tungsten, titanium, zirconium, the carbides, the borides and'the nitrides of each metal with a powdered ductile metalselected from the group consisting of copper and lead, filling through the die to a mold the powdered mixture to form a hollow shaped charge line, subjecting the case powdered mixture in the die to apressure of at least 150,000 lbs. to form a pressed cone shell, sintering the pressed conical liner at a temperature between the melting points of the refractory material and the ductile metal, repressing the sintered conical liner in a suitable die to increase the density, resintering the repressed liner to obtain a' shaped charge liner of near maximum density containing 3% to 25% of the ductile metal.

6.;A method of forming a hollow shaped charge liner from powdered material comprising, filling through a die to a mold of the desired cone shape a powdered refractory material selectedfrom a group consisting of tungsten, titanium, zirconium, the carbides, the borides and the nitrides of each metal, compressing the powdered material in the die to a pressure of at least 150,000 lbs. to form a pressed shaped charge liner, removing the pressed liner from the die, sintering the pressed conical liner in a non-oxidizing atmosphere to form a porous structure of the pressed powder, infiltrating the porous structure of the liner to increase the density with a molten ductile metal selected from a group consisting of copper and lead by heating at a temperature below the first sintering temperature but above the melting point of the ductile metal and cooling the infiltrated shaped charge liner of refractory material to produce a hollow shaped charge liner of near maximum density and containing 3% to 25% of the ductile metal.

References Cited UNITED STATES PATENTS Schwarzkopf 75208 G'oetzel 75208 X Lawson 10224 Grubel 75268 X Day 75208 X Cartier 75214 X Caldwell 102-214 Charrin 102-214 Charrin 102214 BENJAMIN R. PADGETT, Primary Examiner. 15 A. J. STEINER, Assistant Examiner. 

